THETELEPHONERANGINMYMEXICOCITY hotel room at about 10:30 p.m. on July 4. The caller was a young woman I’ve known since she was a child: Aleida Alavez, a city councilwoman representing the Partido de la Revolución Democratica ( PRD), the party of Andrés Manuel López Obrador (or “ AMLO,” as he’s known), the presidential candidate who’d lost the balloting by half a percentage point two days earlier and was now challenging the results of Mexico’s national election.

“You told me that if we send people into the field, you want to go,” she said. “Be at Mitla at eleven. Alejandro will pick you up. You’ll be going to Puebla.” Her call reminded me of those that must have gone out when American electoral processes went awry in Florida in 2000. But the Mexican contest was far more bitter than the tiff between George W. Bush and Al Gore. It was essentially a battle between the prosperous and the struggling—a class war.

Mexico has been a democracy, it is now generally conceded, only since 2000, when Vicente Fox was elected president. Before that, elections were noncontroversial, their winners known months ahead of time. All of them came from the Partido Revolucionario Institucional ( PRI). Only once before, in 1988, had a candidate backed by the poor—Cuauhtemoc Cárdenas, of what would become the PRD—challenged the country’s oligarchy, but that election, it is widely believed, had been stolen by Carlos Salinas, of the PRI. This year’s polls showed a divide like that of 1988, with blue-collar workers backing López Obrador and the PRD, white-collar workers split in their loyalties, and the moneyed classes lined up behind Felipe Calderón and the Partido Acción Nacional ( PAN)—Fox’s party. Late polls had predicted a close finish. Militants from the PRD had vowed that, no matter the cost, they would not let an election be stolen again. On the night Aleida called, they were convinced that a steal was under way.

I knew that Mitla referred not to the Oaxacan town famous for its ruins but instead to the street where López Obrador’s party had one of its offices. But I assumed that by “Puebla,” Aleida meant the city some eighty miles southeast, home to Mexico’s Volkswagen plant. I was wrong. At Mitla I would begin a forty-hour trip that would reacquaint me with rural Mexico in the raw and teach me much about how Mexican politics works today.

I showered, threw my Dopp kit into a backpack, and, thinking I’d be gone only overnight, left the hotel.

The PRD office on Mitla Street is a three-story building that was a sixties mansion. A sliding metal door on its ground floor, a garage space, was half-open when I arrived. A clutch of about a dozen men and women who looked like white-collar workers and block-captain types was gathered around the desk of a uniformed guard.

“Are you going to Puebla with us?” someone asked me as I stepped inside.

“I am supposed to meet Alejandro,” I said, addressing the guard.

“Go upstairs,” he said.

The receptionist on the third floor, still on duty, motioned me into an office where a dozen more volunteers had gathered. They were standing, arms folded, watching a late-night TV show: Gray-haired but baby-faced AMLO, 52, was the guest.

Before the program was over, Alejandro Ojeda appeared, fresh from a PRD strategy meeting. The group split into two, both bound for Puebla, but Alejandro and I descended the stairs alone and got into his SUV. It was pitch-black outside.

I’d first met Alejandro ten years earlier, when he was a law student and Aleida’s suitor. The years had been kind to him. His limbs were thicker, and a little gray had come into his hair, but it’d done him good. Dressed in a buttoned-up cotton shirt and casual slacks, he had the look of a bronze crooner of syrupy love songs or of a suave, smooth-skinned movie star. He always smiled more than he talked, and he said almost nothing as we drove.

In another residential neighborhood, its curbs lined with cars, we came upon a stretch of sidewalk bathed in yellow light: a second house-turned- PRD-office. Six people were gathered outside. Inside, more than sixty volunteers, most of them in their thirties, were staring at computer screens placed on top of collapsible tables. A nine-year-old boy sat at one of the tables, playing a computer game. The plastered interior walls of the office were painted a pale yellow. Fluorescent lights, four feet long, were mounted in fixtures in the ceiling, their wires encased in conduit, as if the place had been rezoned for commercial use.

The volunteers were looking for irregularities in actas de escrutinio, or “voting tally reports,” by scrolling through the Web pages of the Instituto Federal de Elecciones. The IFE is a bureaucracy that was created in 1990, following the Cárdenas-Salinas election, to give credibility to the Mexican electoral process.

It was the IFE that had announced, at 11:00 p.m. on the night of the election, that the 2006 presidential race was too close to call. In his televised message to the nation, IFE president Luis Carlos Ugalde instructed the candidates not to make any declarations until the results had been announced. But within thirty minutes, both AMLO and Calderón had proclaimed victory anyway. Despite the nearly real-time flow of official data, the outcome wasn’t clear by early morning. The capital’s newspapers ran headlines like “Who?” “Wait!” and “Uncertainty Reigns.”

By mid-afternoon on July 3, the IFE’s Web site had pointed to a winner. With 98.45 percent of the vote reported, Calderón led by 1.04 percent. But by then, López Obrador, known to the masses as El Peje—after a garlike fish from his native state of Tabasco—had already lobbed his first grenade. The IFE’s calculations, he charged, were 3 million votes short; its numbers totaled only 39 million when, according to its own records, nearly 42 million Mexicans had voted.